The following disclosure relates to electrical circuits and signal processing.
Electronic circuits typically operate using a constant supply voltage. A voltage regulator is a circuit that can provide a constant supply voltage, and includes circuitry that continuously maintains an output of the voltage regulator—i.e., the supply voltage—at a pre-determined value regardless of changes in load current or input voltage to the voltage regulator. One type of voltage regulator is a linear regulator. A linear regulator typically operates by using a voltage-controlled current source to force a fixed voltage to appear at an output of the linear regulator.
FIG. 1 shows a conventional linear regulator 100 that provides a regulated output voltage VOUT from a power source voltage VPOWER. Power source voltage VPOWER can be supplied from a transformer (not shown). Linear regulator 100 includes a voltage-controlled current source 102, sense circuitry 104, a load capacitor CL, and a resistive load RLOAD. Sense circuitry 104 senses output voltage VOUT, and adjust voltage-controlled current source 102 (as required by the resistive load RLOAD) to maintain output voltage VOUT at a desired value (e.g., 5 volts). Load capacitor CL compensates for variations in a load current ILOAD.
Conventional linear regulators are generally quite stable, however, in circumstances that a linear regulator receives a power source voltage (e.g., VPOWER) that is outside of (e.g., exceeds) the operating range of the linear regulator, stress problems may occur and the linear regulator may break down. For example, a linear regulator fabricated through a 5 volt CMOS process may break down if an associated power source (e.g., a transformer having large output fluctuations) supplies a power source voltage to the linear regulator that is greater than 6 volts.